Is Electron Spin Change Possible?

• physicsnewb7
In summary, electron spin can change in terms of its projection on a given axis, but the absolute value of its spin remains constant. This change can occur through interactions, collisions, and exposure to external magnetic fields. However, the electron's spin is a fixed property and cannot be changed in magnitude. It is also incorrect to describe a single electron as paramagnetic or diamagnetic, as these are properties of bulk materials. Spin and magnetic fields are closely related, and the field of Spintronics explores this relationship. The allowed z-component values for a delta baryon with spin 3/2 are 3/2, 1/2, -1/2, and -3/2, with units of \hbar.

physicsnewb7

Can electron spin change? If so how does this happen?

the direction of its spin will precess around an externally applied magnetic field. also it can change from diamagnetic to paramagnetic.

physicsnewb7 said:
Can electron spin change? If so how does this happen?

When people talk about spin then may mean two different things. One is the absolute value of spin (the length of the vector). For the electron this value is $$\hbar/2$$, and it never changes, i.e., this is a fixed property of the electron, like its mass or charge.

Another thing is spin projection on a given axis (a vector component). This projection may be either $$+\hbar/2$$ or $$-\hbar/2$$, with probability weight assigned to each value. These probabilities may change in electron interactions, collisions, etc.

It is correct that the orientation of the electron spin can be changed.

It is incorrect to describe a single electron as paramagnetic or diamagnetic. These are properties of bulk materials, not individual electrons.

well yes. I was speaking loosely. but the electron will either align with or against the applied magnetic field. this is analogous to para and diamagnetism.

Grampa, for heaven's sake, please turn your fount of misinformation down a notch.

First, as I said before, it is incorrect to describe a single electron as paramagnetic or diamagnetic. These are properties of bulk materials, not individual electrons. Second, the only person discussing applied magnetic fields is you. Third, the terms describing the orientation of spins with respect to external fields is not para- and dia-, but rather para- and ortho-.

The electron cannot change the magnitude of its spin or its magnetic moment. In the hydrogen atom, it is in the field of the proton spin (much weaker). There are only two alignments permitted; same direction, and opposite direction, They differ by 1420 MHz (21 cm). This is perhaps the most dominant microwave emission (and absorption) line in the universe.

meopemuk said:
When people talk about spin then may mean two different things. One is the absolute value of spin (the length of the vector). For the electron this value is $$\hbar/2$$, and it never changes, i.e., this is a fixed property of the electron, like its mass or charge.

Another thing is spin projection on a given axis (a vector component). This projection may be either $$+\hbar/2$$ or $$-\hbar/2$$, with probability weight assigned to each value. These probabilities may change in electron interactions, collisions, etc.

So the magnitude of the vector doesn't change but it's components do in a conservative way so as to keep a constant spin magnitude of h/4pi.

physicsnewb7 said:
So the magnitude of the vector doesn't change but it's components do in a conservative way so as to keep a constant spin magnitude of h/4pi.

That's right.

Grampa, for heaven's sake, please turn your fount of misinformation down a notch.

First, as I said before, it is incorrect to describe a single electron as paramagnetic or diamagnetic. These are properties of bulk materials, not individual electrons. Second, the only person discussing applied magnetic fields is you. Third, the terms describing the orientation of spins with respect to external fields is not para- and dia-, but rather para- and ortho-.

Pure physicists may not be aware of it, but the only real practical manifestation of spins is exposed by applying some equivalent of an external magnetic field to the device.

That basically takes spin (and all the entailing theoretical discussion) out of the Hilbert space and shows that it's real and it could be used.

The fact that Grampa's referring to - precession of spin - is the basis of the first proposed spinFET in 1989 by Datta and Das. In fact, spin and magnetic fields are so entangled that the entire field of Spintronics (crowned by its first Nobel prize in 2007) is founded upon those two.

I'd go easy with Grampa if you haven't read a sentence involving spins and applied magnetic fields. Because that's your fault.

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meopemuk said:
When people talk about spin then may mean two different things. One is the absolute value of spin (the length of the vector). For the electron this value is $$\hbar/2$$, and it never changes, i.e., this is a fixed property of the electron, like its mass or charge.

Another thing is spin projection on a given axis (a vector component). This projection may be either $$+\hbar/2$$ or $$-\hbar/2$$, with probability weight assigned to each value. These probabilities may change in electron interactions, collisions, etc.

Great answer and insight.

This must be a sticky post to every spin question. first understand what you are talking about:

i) Is it the spin vector (projection)?
ii) Or is it simply the magnitude of that?

The first one will be important when magnetization and EXTERNAL magnetic fields are present

meopemuk said:
One is the absolute value of spin (the length of the vector). For the electron this value is $$\hbar/2$$, and it never changes, i.e., this is a fixed property of the electron, like its mass or charge.

Isn't it $\sqrt{3}\hbar/2$? It's actually in an eigenstate of S2, right?

No, the electron's spin is $$\frac{\hbar}{2}$$

It is in an eigenstate of $$S^2$$ with eigenvalue $$\frac{\hbar^2}{4}$$. Take the square root of that and you get the correct answer.

Why isn't the eigenvalue $\sqrt{S(S+1)}$?

Matterwave said:
No, the electron's spin is $\frac{\hbar}{2}$

No, the "z-component" (actually the component along any direction) of the spin angular momentum vector has that value (either + or -).

The magnitude of the spin angular momentum vector is a fixed $\sqrt{3} \hbar / 2$.

http://hyperphysics.phy-astr.gsu.edu/Hbase/spin.html

Ah, you are indeed correct. I was wrong. Sorry.

Indeed, I had forgotten that the spin can never point directly in the +/- z direction.

so what are the allowed z-component values for a delta baryon? (spin 3/2)

3/2, 1/2, -1/2, -3/2

thank you. :-)

Matterwave said:
3/2, 1/2, -1/2, -3/2

Don't forget to multiply by $\hbar$ if you're talking about the physical quantity (angular momentum) and not the quantum number.

I think the hbar is assumed. I mean, numbers don't have units...so...but if you want to be pedantic alright.

$$\frac{3\hbar}{2}, \frac{\hbar}{2}, \frac{-\hbar}{2}, \frac{-3\hbar}{2}$$

1. Can an electron's spin direction be changed?

Yes, an electron's spin direction can be changed through various physical interactions, such as electromagnetic fields or collisions with other particles.

2. What causes an electron's spin to change?

An electron's spin can be changed by external influences, such as interactions with other particles or exposure to magnetic fields.

3. Can an electron's spin direction be controlled?

Yes, an electron's spin direction can be controlled through precise manipulation of its environment, such as applying a strong magnetic field or using quantum technologies.

4. Does an electron's spin always change in the same direction?

No, an electron's spin direction can change in either a clockwise or counterclockwise direction, depending on the specific interaction or manipulation.

5. Is it possible to change the spin of an individual electron?

Yes, it is possible to change the spin of an individual electron using advanced techniques such as spin-polarized scanning tunneling microscopy or quantum information processing.